Sustainable development in WPCBs treatment for production of bituminous waterproofing materials

Abstract

Due to the rapidly increasing use of electrical devices, e-waste became one of the major threats to the environment. Waste printed circuit boards (WPCBs) are an integral part of electrical devices, thus the interest in their recycling is growing. Recycling of WPCBs can be performed by applying hydrometallurgical or pyrometallurgical processes, as well as vacuum pyrolysis. The main advantages of vacuum pyrolysis are eco-friendliness, economic viability and efficiency in extracting present noble metals, while pyrolysis oil occurs as a by-product. Pyrolysis oil poses a tremendous threat to the environment, due to the possibility of its spillage into water, as well as a potential release into the air and soil. Because of this, the pyrolysis oil was subjected to chemical treatment with different reagents, such as sodium hydroxide, calcium oxide, sulfuric acid and maleic anhydride, with the intent to solidify the material and remove unpleasant odors. Incorporation of the solidified materials into bitumen, at 2.5, 5, 7.5, and 10 wt.% addition, was performed to obtain waterproofing materials. The obtained solidified and bituminous water-resistant materials were subjected to various test methods: FTIR spectroscopy, physicochemical and mechanical properties of bitumen, etc. which showed that all the tested characteristics are in accordance with values prescribed by the current standard. Toxicity Leaching Procedure (TCLP) confirmed non-hazardous characteristics of the obtained materials, except for the ones with added solidified pyrolysis oil, with Sodium hydroxide, that showed higher leaching of the phenol constituent.